The present invention relates to the correction of a binary image to compensate for differences in printer responses. More specifically, the present invention relates to the correction of a binary electronic image file so that a target printer prints a binary image similar to another printer, such as the printer for which the binary image was originally created.
The quality of a printed image from a binary image file depends significantly on the compatibility between the conditions surrounding the creation of the binary file and the tone reproduction characteristics of the printer. When electronic binary images are created by a binary image creation device, such as a scanner, the device may create the image with a specific printer model in mind. For example, a scanner may scan an original image at a desired resolution and assign gray image data such as relative darkness numbers from 0 to 2n for each pixel, where 2n is the number of gray gradations. To create a binary image, that information may undergo half-toning or error diffusion and be converted into a binary format, where each binary pixel is assigned a 0 or a 1. During the process from the initial scanning to the final creation of the binary file, a tone response of a specific printer model is typically assumed.
As each printer has a different tone response, the same binary image will appear different when it is printed on different printers. In fact, the printing of binary images by printers for which they were not originally generated can cause many image quality problems, such as darkness shifts, spotting or mottling, and half-tone break-up. However, in today""s electronic age with more scanners and printers becoming available on network systems, the printer that is used to print an binary image is rarely the printer for which the image was specifically created. Therefore, the print quality of many of these images suffers.
This problem is further magnified when the resolution of the printer at which the image is printed does not match the resolution of the image when it was originally created. When the resolution of the image is changed, image imperfections, such as density inconsistencies, scaling errors, Moire artifacts, and darkness shifts, that give the image a different appearance can be further magnified when they are printed on a printer for which they were not specifically created. While, prior patents, such as U.S. Pat. Nos. 5,553,171, 5,270,836, 5,363,213 and 5,226,094, partially corrects these image imperfections, they do not solve them entirely or address the problem when the image is printed on a printer for which it was not intended. A solution was thus needed to ensure print consistency of binary images across printing devices and when printing on a printer other than the printer for which the binary image was created.
On some occasions when a user desires to print a specific binary image, the user may be fortunate enough to be able to have access to the printer that was the originally-intended printer for that image. However, it is well known that printers are not 100% reliable, and replacement or substitute printers of a different type may be used during temporary periods. The replacement and substitute printers may therefore be subject to the image quality problems described above. A solution to make replacement or substitute printer like the originally-intended printer was thus needed.
Further, there may be situations where a user prefers the image quality of a specific binary image printed on a specific or desired printer over the originally-intended printer or any other printer. For example, the preferred printer may exaggerate or lessen the contrast of features in the image as compared to the originally-intended printer, and may not be adversely affected by any image quality problems. Thus, the user may want the originally-intended printer or any other printer to model the responses of another known printer. Further, there may be other circumstances where a user desires one printer to behave like another. This may even occur when the binary image is not formed with a specific printer model in mind or when the user is not aware of the specific printer model assumed by the scanner. In such cases, the user may just want one printer to emulate the results obtained by a different printer. However, the prior art fails to include a solution that satisfies these objectives. Accordingly, such a solution was needed.
Accordingly, it is an object of the present invention to provide a method and a system which overcomes the limitations of the prior art.
It is an object of the present invention to correct binary images so that a printer, other than the one which the image was created for, can provide enhanced print quality. The invention accomplishes this in such a way that a target printer can mimic the response quality of the printer for which the image was created.
It is an object of the present invention to modify binary images so that the quality of the images that are ultimately printed becomes more of a function of the original images themselves and less of a function of differences in printers and printer responses.
It is an object of the present invention to provide a method for altering a print-ready binary image file. The method includes converting the print-ready binary image file to gray scale image data so that each pixel has a grayness value. The grayness value of the pixels of the gray scale image data are altered based on a relationship between a plurality of printer reproduction curves. The gray scale image data with the altered pixel grayness values is converted to a binary image file.
It is another object of the present invention to provide a method for altering a print-ready binary image file. The method includes providing a print-ready binary image produced by a process utilizing a first printer reproduction curve. The print-ready binary image is converted to gray scale image data, which is modified based on the difference between the first printer reproduction curve and a second reproduction curve. The modified gray scale image data is converted back into a binary image file.
It is yet another object of the present invention to provide a system for altering a print-ready binary image file so that it produces desired printed results from a target printer. The system includes print and scan circuitry, tone reproduction correction circuitry, and binarization circuitry. The print and scan circuitry receives the print-ready binary image file and converts the print-ready binary image file to gray scale image data wherein each pixel has a grayness value. The tone reproduction correction circuitry is functionally coupled to the print and scan circuitry and to the binarization circuitry. The tone reproduction correction circuitry alters the grayness value of the pixels of the gray scale image data based on a relationship between a plurality of printer reproduction curves. The binarization circuitry converts the gray scale image data with the altered pixel grayness values back into a binary image file.